.nav_header {
  height: px2rem(64px);
  border-bottom: 1px solid #b2b2b2;
  position: fixed;
  width:100%;
  top: 0;
  z-index: 99;
  background-color: #fff;
  .nav_title{
     font-size: px2rem(17px);
     color: #2f2f2f;
     text-align: center;
     line-height: px2rem(73px);
  }
  .nav_icon {
    width: px2rem(27px);
    height: px2rem(27px);
    background-image: url('./img/back.png');
    background-size: cover;
    position: absolute;
    top: px2rem(23px);
    left: px2rem(10px);
  }
}